git-check-ref-format: clarify documentation for --normalize

Use of 'iff' may be confusing to people not familiar with this term.

Improving the --normalize option's documentation to remove the use of
'iff', and clearly describe what happens when the condition is not met.

Signed-off-by: Damien Regad <dregad@mantisbt.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-check-ref-format.txt b/Documentation/git-check-ref-format.txt
index 8611a99..92777ce 100644
--- a/Documentation/git-check-ref-format.txt
+++ b/Documentation/git-check-ref-format.txt
@@ -100,10 +100,10 @@
 --normalize::
 	Normalize 'refname' by removing any leading slash (`/`)
 	characters and collapsing runs of adjacent slashes between
-	name components into a single slash.  Iff the normalized
+	name components into a single slash.  If the normalized
 	refname is valid then print it to standard output and exit
-	with a status of 0.  (`--print` is a deprecated way to spell
-	`--normalize`.)
+	with a status of 0, otherwise exit with a non-zero status.
+	(`--print` is a deprecated way to spell `--normalize`.)
 
 
 EXAMPLES